Method and device for isolating an electro-conductive flowing medium

ABSTRACT

A voltage isolating device selectively electrically isolates from each other two points ( 13  and  15 ) of an electrically conductive flow medium having different electrical potentials along a flow path. The electrically conductive flow medium is conveyed in the inner space ( 18 ′) of a freely protruding carrier ( 17 ′) having at least one discharge opening ( 29 ). The carrier ( 17 ′) moves back and forth between a first isolating position and a second docking position to allow a transfer flow. The discharge opening ( 29 ) is closed until the docking position has been reached, wherein the discharge opening is opened, and is closed again when the carrier is moved out of the docking position.

TITLE OF THE INVENTION FIELD OF THE INVENTION

The invention relates to a method and a device for isolating points ofan electrically conductive flow medium having a different electricalpotential along its flow path, for example in an electrostatic paintingsystem.

BACKGROUND INFORMATION

Methods and devices of the known art are technically complex,particularly if the flow medium is at ground potential at the beginningof its flow path and has high voltage applied to the flow medium at theend of its flow path. Such relationships dominate, for example, inelectrostatic painting systems that process water-thinnable paints orlacquers, as are used, for example, in automobile manufacturing. In suchelectrostatic painting systems, paint or lacquer material is guidedthrough a conduit or line to an atomizer or spray apparatus that isunder a high voltage potential. If this paint or lacquer material iselectrically conductable, it is important that an electrical short doesnot occur along the paint supply line, as the other end of the paintsupply line is at ground potential. For this reason, a high voltagepotential must also be applied to the paint supply line and thecorresponding paint containers and the line, and the containers must besecured in a high voltage area to which access is prohibited. This, onthe other hand, has as a consequence that the containers cannot berefilled from a supply line that is at ground potential duringoperation. As a result, the paint operation must be interrupted duringthe refilling procedure.

In order to ensure a continuous supply of the paint or lacquer materialfrom a container under a high voltage potential to the atomizer or sprayapparatus, the container must be filled discontinuously with paint orlacquer material in a suitable manner. This is in fact the actualpractice with existing paint systems. As a further complication,generally several different colors or tones of the conductive paint orlacquer such as, for example, water-based lacquer, must be held readyfor delivery to an atomizer or spray apparatus that is under highvoltage via an automatic color changer. If voltage isolating devices areused between the color changer and the atomizer or spray apparatus, itis known that it is then impossible to quickly automatically flush allthe components if the voltage isolating devices allow only shortdistances between the components under different potential during thepainting operation, and if the devices are also to be constructed ascompactly as possible.

In order to provide the necessary isolation in view of the governingpotential between the components that are under high voltage and atground potential, relatively large spaces or distances in the range ofgreater than 200 mm must be adhered to during the painting operation.Otherwise, the components cannot be switched between the inputs andoutputs during the grounded operation, free of high voltage, to allow anautomatic quick color change or a flushing cycle to be carried out.

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to provide measures thatwill allow a particularly practical handling and reliable isolationbetween points of the flow path and/or of the electrically conductiveflow medium that are under different potential.

The above objects have been achieved according to the invention in avoltage blocking device for conveying an electrically conducting fluidtherethrough, comprising: a housing including a housing outer wall and afirst intermediate wall, wherein a first chamber and a second chamberare provided on opposite sides of the first intermediate wall within thehousing outer wall, and wherein an annular receiving channel and anoutlet opening are provided in the housing; an electrically insulatingliquid contained in the second chamber; a movable nozzle needle having afree first end that is movably arranged in the housing and that hastherein at least one radially extending discharge opening, and having alongitudinal channel that extends longitudinally axially in the movablenozzle needle and that communicates with the at least one radiallyextending discharge opening, wherein the free first end of the nozzleneedle is movable between a first position and a second position withinthe housing, and wherein the free first end in the second position islocated in the second chamber containing the electrically insulatingliquid; a first drive connected to the movable nozzle needle and adaptedto move the movable nozzle needle selectively between the first positionand the second position; a first closure member that is movably arrangedand guided in the first intermediate wall so as to selectively open andclose the annular receiving channel; and a second closure member that ismovably arranged so as to selectively open and close the at least oneradially extending discharge opening in the free first end of the nozzleneedle. In a particular embodiment of the invention, the annularreceiving channel and the outlet opening are especially arranged in theintermediate wall. According to another embodiment feature of theinvention, a further annular drainage channel is provided axially nextto the annular receiving channel.

With the inventive arrangement, this means that the electricallyconductive flow medium flows inside of a lance or nozzle needle that hasa discharge opening and that moves between an isolating position and adocking position which allows the transfer flow of the flow medium, andback again. The discharge opening remains closed until the dockingposition has been reached. Thus, the electrically conductive fluid doesnot come into contact with the contacting walls so that the danger islow that a film of electrically conductive fluid will build up on thecontacting surfaces and then lead to a short-circuit. Furthermore, thevoltage-blocking valve that serves as the voltage-blocking devicepreferably has an electrically non-conductive fluid in the chamber thatreceives the lance or nozzle needle (also called the valve needleherein).

The voltage-blocking valve according to the invention further comprisesend pieces for the flow path that can be connected to each other andreleased from each other, whereby these end pieces are arranged at thesame time in the electrically non-conductive fluid. It is thereforepossible to provide a voltage-blocking device that satisfies high safetyrequirements, yet is small in size, is simple to use, provides greatswitching speed, and is also practical in its handling.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, based on an exampleembodiment below that is represented in the drawing. Shown are:

FIG. 1 a sectional view of a voltage-blocking device in its openedstate;

FIG. 2 a sectional view as shown in FIG. 1, shortly before closing theflow path; and

FIG. 3 a detail of the device shown in FIGS. 1 and 2, drawn to a largerscale, with a closed flow path.

DETAILED DESCRIPTION OF A PREFERRED EXAMPLE EMBODIMENT OF THE INVENTION

A voltage-blocking device according to the example embodimentrepresented in the FIGS. 1 to 3 is a device that is switched as avoltage-blocking valve 1. The voltage-blocking valve 1 comprises amulti-piece housing 2 that consists primarily of an insulating material.The housing 2 comprises a centrally arranged cylindrical housing body 3and covers 6, 7 arranged respectively at both ends 4, 5 that close thehousing 2. Intermediate walls 8 and 9 are arranged in the housing 2spaced apart from each other and from the covers 6 and 7. Theintermediate walls 8 and 9 form on the one hand chambers 10, 11 and 12in the internal space of the housing 2 and further serve for mountingand guiding components with the help of which a flow medium can flowfrom a first point 13 of a flow path 14 to a second point 15. The firstpoint 13 and the second point 15 are at a different electricalpotential, depending on the electrical switching state. The componentsthus serve to connect and interrupt the flow path 14 of the electricallyconductive flow medium.

According to the example embodiment shown in the figures, the componentthat forms the first point 13 is the free end 16 of a nozzle needle 17,also called a valve needle 17 herein. The valve needle 17 has alongitudinal canal 18 and is connected, for example, to a line that hasa low electrical potential. Accordingly, the flow medium that is then inthe valve needle 17 has a low electrical potential.

Furthermore, a drive 19 is allocated to the valve needle 17 that acts onthe valve needle 17 to move it relative to the second point 15, whichcomprises components that can be connected to and released from eachother. This drive 19 comprises pistons 20 and 21 that can be pressurizedvia the connectors 22 and 23 so as to move the valve needle 17 in atleast two directions, as can be seen in the figures. Compressed air thatis supplied via the lines 27 or 27A serves as the pressure medium.

The free end 16 of the valve needle 17 (FIG. 1) is located in the middlechamber 11 that is always filled with isolating fluid and is closed atthe endface according to the example embodiment. The flow path 14 or thelongitudinal canal 18 terminates in the valve needle 17 at at least onedischarge opening 29 that is radially oriented, which can be seenparticularly in the representation in FIG. 3, drawn to a larger scale.An annular channel 30 is allocated to the one or more radially orienteddischarge openings 29 and forms a receiving opening on the housing sideand leads to a delivery port 31 that is oriented externally. The annularchannel 30 is disposed in the intermediate wall 8 and is arranged suchthere that it is covered by a closure 32 when the voltage-blocking valve1 is open, according to FIG. 1. This closure 32 is movable relative tothe valve needle 17 and arranged along the axis of the valve needle 17.Pressure is applied to the closure 32 in the closing direction (FIGS. 1and 2) by the force of pressure of a spring 33, for example. The closure32 has a recess 34 on its endface facing the valve needle 17. Acentering piece 35 at the free end 16 of the valve needle 17 projectsinto the recess 34 initially when the voltage-blocking valve 1 isclosed, as shown in FIG. 2. When, however, the valve needle 17 is pushedstill farther from the position shown in FIG. 2 in the axial directiontoward cover 6, the closure 32 moves to the left into the position shownin FIG. 3 until it releases the annular channel 30. At the same time thedischarge openings 29 of the longitudinal canal 18 of the valve needle17 move from their position of FIG. 2 to the left until they arepositioned in front of the annular channel 30 (FIG. 3).

As shown in FIG. 3, the discharge openings 29 are covered by a sleeve 50that is axially slidable along the valve needle 17. A pressure spring 51applies pressure to this sleeve 50. The sleeve 50 furthermore has a stop52. Directly before the discharge openings 29 reach the annular channel30, the stop 52 contacts a resistance so that the sleeve 50 can nolonger move in the axial direction to the left despite further movementof the valve needle 17. This releases the discharge opening 29 (FIG. 3).Now, the flow medium, that is, the electrically conductive fluid, canflow through the valve needle 17 to the delivery port 31 arranged in theside of the housing. Thus, the valve needle 17 forms an end piece of theflow path 14. The second end piece of the flow path 14 is arranged onthe housing side.

The valve needle 17 is a hollow valve needle or a freely protrudingcarrier 17′ with an inner space 18′ through which the electricallyconductive flow medium flows. This carrier 17′ itself moves between afirst or isolating position and a docking position shown in FIG. 3. Theelectrically conductive fluid can flow when the carrier 17′ is in thedocking position. Basically, the carrier 17′ retracts again as soon asthe transfer flow operation has concluded. The discharge openings 29 onthe free end of the carrier 17′ are only open in the docking positionand are otherwise closed by the sleeve 50 that serves as a closure onthe side of the movable valve needle 17. In a comparable manner theannular channel 30 arranged on the housing side is always then closedwith the aid of the closure 32 when the valve needle 17 is in theisolating position and is only then open when the valve needle 17 hasreached the docking position. This means essentially that theelectrically conductive fluid flows without contact with the limitingwalls that move relative to each other when the voltage-blocking deviceopens and closes.

The flow path 14 is formed on the housing side by the annular channel 30and the allocated delivery port 31. It shall be further understood thatthe direction of flow for the electrically conductive flow medium canalso be oriented in the opposite direction.

As can be seen in the example embodiment represented in the figures, apiston 36 disposed in the chamber 10 is allocated to the closure 32 andis supplied with a pressure medium via a line 37.

Furthermore, an axially aligned relief bore 39 is disposed in theclosure 32 so that the centering piece 35 can protrude into the recess34, gap-free, when the valve needle 17 is docking.

Finally, seal elements 40 (FIG. 2) are required at all pistons and theclosure 32, as well as between the covers 6 and 7 and the variousassembled parts, and also to seal the valve needle 17. The seal elements40 are shown in the figures. A seal element 41 arranged on an endface ofthe sleeve 50 is particularly significant. The seal element 41 contactsthe endface of the centering piece 35 facing it after leaving thedocking position according to FIG. 3.

Furthermore, according to the example embodiment, two seal elements 42and 43, spaced a distance from each other, encircle the sleeve 50 in itsdocked state. The seal element 42 on the annular channel side servessimultaneously as a stripping or wiping element. An annular channel 44disposed between the two sealing elements 42 and 43 in the intermediatewall 8 leads to the previously mentioned line 28 and the connector 25.If necessary, entrained electrically conductive fluid shall be collectedhere and drained off through the connector 25.

The sealing elements shown in the figures and allocated to the closure32, the annular or ring channel and its outflow line possess basicallysimilar function and significance.

All other sealing elements shown in the figures shall not be describedin greater detail here. Basically, the same applies to the separation ofthe housing 2 into various housing components, so that the desiredfunction is ensured. Thus, it is fundamentally possible even in certaincases to operate the voltage-blocking valve 1 according to the inventionwithout an electrically non-conductive fluid because the construction ofthe voltage-blocking valve 1 provides a very high degree of achievableisolation. For this reason, the invention is not limited to theparticular example embodiment shown in the figures. Rather, it is stillpossible to make modifications without deviating from the fundamentalconcept of the invention.

For application in a paint system the invention comprises essentially avoltage-blocking valve that can be arranged between a grounded paintsupply line and a supply container or between the supply container andan atomizer or spray apparatus under high voltage. The paint intakeport, which is at ground potential, is arranged via the fluid isolatingmedium such a short geometrical distance from the paint output port thatis at high voltage. This distance is so short that it can be bridged inthe shortest time when the supply line docks to the paint dischargeport, at which time the switching state provides ground potential toboth sides. Thus, it is possible that different voltage-blocking valvesthat are switched in series, including supply containers that arearranged between the valves, can be integrated into an automatic colorchange and flush or rinse cycle. A completely open and automaticallyflushable supply line can be switched between a grounded paint orlacquer supply hose and the atomizer or spray apparatus. Thevoltage-blocking valve that is constructed as a hollow needle valvecomprises thereby a paint or lacquer supply lance that is slidablyarranged, for example, in the chamber filled with the fluid isolatingmedium under exclusion of air, and at ground potential a short distancefrom a docking station that is alternatively at high voltage or atground potential and that can be introduced into the docking station bya preferably pneumatically actuated thrust device. The docking stationforms a valve that maintains a closed path to a subsequently switchedsupply container as long as the paint supply lance has not docked, andopens the path when the lance docks in such a way that the paint orlacquer material that is available in the hollow needle valve remainsreliably separated from the surrounding isolating medium. This preventsan overflow of paint material into the isolating medium or from theisolating medium into the paint material. The docking station therebyencloses the introduced hollow needle valve airtight and fluid-tight,and the hollow needle valve opens only in the docked state when it isencircled by an outer sleeve of the docking station.

The piston carrying the paint supply lance/valve needle 17 furthermorecleans the inner wall of the chamber that receives the piston fromdeposits as it moves between the docking and the undocking or isolatingpositions. The piston thus serves, with its docking and undockingmovement, simultaneously, as a recirculating pump for the isolatingmedium.

Basically, the longitudinal canal 18 in the valve needle 17 is a freelyprotruding carrier 17′ about the inner space 18′. The carrier 17′ ismovable from an isolating position into a docking position, which thenallows the transfer flow of the electrically conductive fluid to takeplace. The annular channel 30 thereby serves as a receiving opening inthe housing side and is opened only in the docking position. The sameapplies for the discharge opening 29 at the freely protruding carrier17′ or the valve needle 17.

The various parts are manufactured from basically known materials,whereby insulating materials can also be used in part.

What is claimed is:
 1. A voltage blocking device for conveying an electrically conducting fluid therethrough, comprising: a housing (2) including a housing outer wall and a first intermediate wall (8), wherein a first chamber (10) and a second chamber (11) are provided on opposite sides of said first intermediate wall (8) within said housing outer wall, wherein an annular receiving channel (30) and an outlet opening (31) are provided in said housing, and wherein an annular drainage channel (44) is provided in said housing axially next to said annular receiving channel (30); an electrically insulating liquid contained in said second chamber (11); a movable nozzle needle (17) having a free first end that is movably arranged in said housing and that has therein at least one radially extending discharge opening (29), and having a longitudinal channel that extends longitudinally axially in said movable nozzle needle and that communicates with said at least one radially extending discharge opening (29), wherein said free first end of said nozzle needle is movable between a first position and a second position within said housing, and wherein said free first end in said second position is located in said second chamber containing said electrically insulating liquid; a first drive (19, 20, 21) connected to said movable nozzle needle and adapted to move said movable nozzle needle selectively between said first position and said second position; a first closure member (32) that is movably arranged and guided in said first intermediate wall so as to selectively open and close said annular receiving channel (30); and a second closure member (50) that is movably arranged so as to selectively open and close said at least one radially extending discharge opening (29) in said free first end of said nozzle needle.
 2. The voltage blocking device according to claim 1, wherein, in said first position, said first closure member (32) is moved away from said annular receiving channel (30) so as to open said annular receiving channel, said second closure member (50) is moved away from said at least one radially extending discharge opening (29) so as to open said at least one radially extending discharge opening, and said free first end of said movable nozzle needle is located so that said at least one radially extending discharge opening communicates with said annular receiving channel which further communicates with said outlet opening (31), to establish a continuous flow path between said longitudinal channel of said movable nozzle needle and said outlet opening; and wherein, in said second position, said first closure member closes said annular receiving channel, said second closure member closes said at least one radially extending discharge opening, and said free first end of said movable nozzle needle is surrounded by said electrically insulating liquid in said second chamber.
 3. A voltage blocking device for conveying an electrically conducting fluid therethrough, comprising: a housing (2) including a housing outer wall and a first intermediate wall (8), wherein a first chamber (10) and a second chamber (11) are provided on opposite sides of said first intermediate wall (8) within said housing outer wall, and wherein an annular receiving channel (30) and an outlet opening (31) are provided in said first intermediate wall (8); an electrically insulating liquid contained in said second chamber (11); a movable nozzle needle (17) having a free first end that is movably arranged in said housing and that has therein at least one radially extending discharge opening (29), and having a longitudinal channel that extends longitudinally axially in said movable nozzle needle and that communicates with said at least one radially extending discharge opening (29), wherein said free first end of said nozzle needle is movable between a first position and a second position within said housing, and wherein said free first end in said second position is located in said second chamber containing said electrically insulating liquid; a first drive (19, 20, 21) connected to said movable nozzle needle and adapted to move said movable nozzle needle selectively between said first position and said second position; a first closure member (32) that is movably arranged and guided in said first intermediate wall so as to selectively open and close said annular receiving channel (30); and a second closure member (50) that is movably arranged so as to selectively open and close said at least one radially extending discharge opening (29) in said free first end of said nozzle needle.
 4. The voltage blocking device according to claim 3, wherein, in said first position, said first closure member (32) is moved away from said annular receiving channel (30) so as to open said annular receiving channel, said second closure member (50) is moved away from said at least one radially extending discharge opening (29) so as to open said at least one radially extending discharge opening, and said free first end of said movable nozzle needle is located so that said at least one radially extending discharge opening communicates with said annular receiving channel which further communicates with said outlet opening (31), to establish a continuous flow path between said longitudinal channel of said movable nozzle needle and said outlet opening; and wherein, in said second position, said first closure member closes said annular receiving channel, said second closure member closes said at least one radially extending discharge opening, and said free first end of said movable nozzle needle is surrounded by said electrically insulating liquid in said second chamber.
 5. The voltage blocking device according to claim 3, wherein said first closure member (32) is cylindrical.
 6. The voltage blocking device according to claim 3, wherein said housing outer wall includes a housing end wall, said movable nozzle needle further has an outwardly protruding second end opposite said free first end, and said movable nozzle needle passes movably through said housing end wall with said outwardly protruding second end of said movable nozzle needle protruding outwardly outside of said housing.
 7. The voltage blocking device according to claim 3, wherein said housing further includes a second intermediate wall (9), said second chamber (11) containing said electrically insulating liquid is bounded between said first and second intermediate walls (8, 9), a third chamber (12) is provided within said housing outer wall on a side of said second intermediate wall (9) opposite said second chamber (11), said first drive comprises a first piston (21) arranged in said third chamber (12) and connected to said movable nozzle needle (17), and said voltage blocking device further comprises a second piston (36) arranged in said first chamber (10) and connected to said first closure member (32).
 8. The voltage blocking device according to claim 3, further having an annular drainage channel (44) provided in said first intermediate wall axially next to said annular receiving channel (30).
 9. The voltage blocking device according to claim 3, further comprising said electrically insulating liquid further contained in said first chamber (10). 